Method of and apparatus for producing a fuel mixture of predetermined calorific value



July 9,1929. R. s. MCNEIL METHOD OF AND APPARATUS FOR PRODUCING A FUELMIXTURE OF PREDETERMINED CALORIFIC VALUE Flled Oct 6 1925 Inventor- IRonaLd $.McNei L y w His Agorneg.

I un h V Patented July 9, 1929.

PATENT I! RONALD S. MCNEIL, OF NEWARK, NEW JERSEY, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

METHOD OF AND APPARATUS FOR PRODUCING A FUEL MIXTURE 0F PREDETER- MINEDCALORIFIC VALUE.

Application filed October 6, 1925. Serial No. 60,920.

My invention relates to automatically maintaining the calorific or heatproducing value of the fuel mixture for a gas burner substantiallyconstant without adjusting or varying the gas and air inlets of theburner to compensate for variations in the density and heating qualityof the gas.

In many manufacturing operations gas and air are mixed in a gas and airmixing chamber under pressure to produce a fuel mixture for a burnerwhich producesa conical blue flame like a Bunsen burner. In incandescentlamp making, for example, Where automatic machinery is used thetemperature of the flame of these burners should be kept as nearlyconstant as possible. In many cases the illuminating gas commonly usedas the gas for the fuel mixture for these burners is a mixture of coalgas. and Water gas. Although the ratio of the coal gas to the Water gasmay vary considerably during the day with variations in conditions atthe gas plant, the gas mixture or illuminating gas delivered by the gasplant is usually proportioned to produce a gas of substantially uniformcalorific or heating value. However coal gas is lighter than water gas,hence as the ratio of one gas to the other changes the density of theilluminating gas changes. Since a light gas flows through an orificemore easily than a heavy gas, a gas and air mixer adjusted to give afuel mixture of a predetermined calorific value with coal gas Will notgive a mixture of the same calorific value with water gas even thoughthe calorific or heat producing value and the pressure of the Water gasand of the coal gas are the same. In order to maintain the heat constantthe burners on the machines were heretofore adjusted from time to timeby hand when the composition of the illuminating gas varied enough toproduce noticeable variations in the heat of the flames.

The object of my invention is to provide a method of automaticallymaintaining the sired uniformity of calorific value and hence of thetemperature of the flames.

In accordance with my invention a conical test flame like that of aBunsen burner, and fed from the same gas and compressed air mains as theWorking flame, is directed against a thin ribbon of metal such asnichrome positioned between the hottest part of the flame and theburner, so as to produce on the ribbon a red hot ring with a dark centerspot. The size of this dark center spot and its temperature varies withthe size and heat of the test flame. Any change in density or incomposition of the gas which alters the calorific valve of the fuelmixture and therefor makes the flame longer or shorter correspondinglychanges the size of this dark spot on the metal ribbon. For example, asthe flame lengthens the dark spot increases in size and the tem peratureof its center falls. A thermo-couple is placed in contact with the metalribbon on the opposite side from the burner and at the center of thedark spot to respond to these changes in temperature due to variationsin the temperature of the test flame, and controls through suitableautomatic mechanism the composition of the fuel mixture supplied to theworking flame in such a Way that the calorific value of the mixture andhence the temperature of that flame remains constant. For example, byvarying the pressure at which the gas is supplied to the gas and airmixing chambers of the burner variations in the heating value of thefuel mixture and in the temperature of the flame can be obtained withouttouching or adjusting the burner.

A variation in temperature which affects the thermo-couple causes avariation in the electromotive force generated by the thermocouple,thereby actuating a voltage responsive device, such as a contact makingvolt meter, which in turn through suitable apparatus controls a pressurereducing valve in the gas mains and thereby varies the pressure of thegas supplied to the mixing chamber for the working burner. In thismanner the gas regulator or heat control mechanism is movedautomatically in response to any variation in the temperature of thetest flame, and quickly varies the gas pressure to bring the calorificvalue of the fuel mixture for the flame back to normal.

, My invent-ion will best be understood in connection with theaccompanying drawing, illustrating diagrammatically one of the manyforms of apparatus which may be used to practice my invention, and inwhich Fig. 1 is a diagram of the gas and air connections to the workingburner, with a control mechanism constructed in accordance with myinvention; Fig. 2 is a view partly in section showing the relation ofthe metal ribbon and thermo-couple to the test burner, Fig. 3 is a sideView showing the relation of the metal ribbon to the flame produced bythe test burner, and Fig. 4 a plan view of the ribbon showing therelative size and location of the thermo-couple, the dark spot on theribbon and the annular zone of higher temperature produced by thetestilame.

In the particular arrangement shown in Fig. 1, working burners 1 aresupplied With a combustible fuel mixture obtained by combining in mixingchambers 2 air from a com pressed air main 3 with gas from a gas main 4.These working burners are of a type generally used and produce a blueconical flame similar to that obtained from a Bunsen burner. The gasmain 4 is fed with gas through a regulator or reducing valve 5consisting of a control valve 6, which is 'moved by a pressureresponsive diaphragm 7 to prevent very wide variations in pressure inthe gas main 4.

A continuous indication of temperature of the flames produced by the gasbeing used in the working burners is obtained by means of a test burner8 supplied from the air and gas mains 3 and 4 and mounted to direct itsblue conical flame against a refractory target, such as a thin metalribbon 9, of nichrome or similar heat resisting alloy, carried in a yoke10.

The ribbon 9 is positioned, as shown in Figs. 2 and 3, so that the tipof the inner blue cone of the Bunsen flame from the burner touches theribbon. The hot spot on the ribbon is in the form, as best shown in Fig.4, of a red hot ring 11 with a dark center spot 12 at a temperature ofabout 320. As the density of the gas and its calorific or heat producingqualities vary the flame from the test burner 8 lengthens and shortens,causing the dark spot 12 to vary in size and in temperature. Athermo-couple 13 secured to the ribbon opposite the test burner at thecenter of the dark spot on the ribbon responds to variations in thetemperature of the dark spot by corresponding variations in theelectromotive force produced by the couple. A suitable couple for thispurpose consists of iron and constantan, which is an alloy consisting ofabout 40% nickel and 60% copper.

The variations intemperature of the spot 12 on the test ribbon 9automatically varies the pressure of the gas in the gas main 4 to theextent necessary to maintain the calorific value of the fuel mixture forthe test and working flames substantially constant without adjustment ofthe burners. Since light gas flows through an orifice easier than heavygas, a mixing chamber correctly adjusted for coal gas will not produce afuel mixture which gives heat enough with water gas at the samepressure. More gas is needed and raisingthe pressure accomplishes thedesired result.

A convenient form of gas pressure control apparatus is illustrateddiagrammatically in Fig. 1, in which the thermo-couple 13 is connectedto a voltage responsive device, such as a contact making volt-meter 1 1,having a movable arm 15 cooperating with two sets of contacts 16 and 17connected to a battery or similar source of current 18 to energizesolenoids 19 and 20. A sensitive volt-meter such as that shown in U. S.Patent No. 1,033,816, July 30,

1912, may be used as a relay responsive to minute voltage variations ofthe thermocouple.

The control valve 6 of the gas regulator is positively moved by thethermo-couple and the voltmeter 14 through some apparatus such as thatillustrated diagrammatically in which a constantly running motor 21drives a worm gear 22 and thereby oscillates a rockingv arm 23 about theshaft 24: of a ratchet wheel 25. Pawls 26 and 27 mounted on the arm 23are controlled by latches 28 and 29 which in turn are controlled by thearmatures of the solenoids 19 and 20. In Fig. 1 the SOlllOld 19 isenergized, and its armature is in position to engage and lift the latch28 as the arm 23 reaches the limit of its counter-clockwise movement,thereby permitting the pawl 26 to drop into place between the teeth ofthe ratchet wheel 25. As the arm 23 moves clockwise the pawl turns thewheel 25 in a clockwise direction. As the arm reverses its direction ofswing the pawl 26 rides upon a tooth of the wheel and is caught by thelatch 28 which holds it inoperative until again released by the armatureof solenoid 19. As long as solenoid 19 is energized the ratchet wheel 25is turned clockwise step by step by pawl 26, and as long as solenoid 20is energized the ratchet wheel is turned step by step in acounter-clockwise direction by pawl 27. When the arm 15 of the voltmeterdoes not touch either set of contacts 16 and 17, and neither solenoid isenergized neither pawl is released, and the arm 23 swings back and forthwithout effect on the ratchet wheel, which remains stationary. The shaft24 controls the regulating valve 6 through any suitable mechanism, suchas a ter spot 12 at a temperature of about 320 C. As the density of thegas varies the flame from the test burner lengthens and shortens and thetemperature of the dark spot 12 varies. These variations are convertedby the volt meter 14 and the valve actuating mechanism into movements ofthe regulator valve 6 of such a character and extent that the pressureof the gas in the gas main 4 is varied sufliciently to bring thecalorific value of the fuel mixture back to normal and hence thetemperature of the flames from the working burner 1 and from the testburner 8 back to normal without any change or adjustment of the burners.Elimination of manual adjustment of the burners is of very greatadvantage in a large factory where a larger number of working burners 1are in use.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is 1. The method of producing a fuel mixture of gas and air ofsubstantially constant and predetermined heat producing value from a gasvariable inits heat producing properties which consists in maintaining aBunsen test flame fed by said gas, producing on a target in said flame,a circular hot spot with a center which varies in temperature withvariations in said test flame, and automatically varying the pressure ofthe gas fed to said fuel mixturein response to variations in thetemperature of the center of the hot I spot produced by said test flameto counteract the temperature change produced by a variation in saidgas.

2. The method of producing a fuel mixture of predetermined calorificvalue from air and a. gas variable in its heat producing value whichconsists in maintaining a Bunsen test flame fed by said gas, producingwith said flame on a target a ring of high temperature varying in sizewith the length of said test flame and automatically varying thepressure of the gas fed to said fuel mixture in response to saidvariations in temperature of said target within said ring of iightemperature.

3. The method of mixing air with gas variable in density to produce afuel supply of constant heating 'value which consists in maintainingatest flame fed from said fuel supply and. having the form of a Bunsenflame, directing the test flame against a target so that the inner bluecone, of the Bunsen .flame impinges upon it to produce a ring of hightemperature with a cooler center spot, and varying the pressure of saidgas in response to variations in temperature of said center spot on thetarget.

4. In a device. of the character described, the combination with asource of fuel supply, of a test burner connected to said source ofsupply and constructed to produce a blue Bunsen flame having an innerblue come, a

metal target mounted in front of said burner to be i-npinged upon by theinner blue cone of the Bunsen flame, a thermal responsive device securedto said target in alignment with the axis of the inner blue cone of theflame, and control mechanism responsive to said thermal responsivedevice for varying the pressure of the fuel in said source of supply.

5. In a device of the character described, the combinationwith a workingburner and a gas main for supplying said burner, of a test burnersupplied from said gas main and constructed to produce a blue Bunsenflame having an inner cone, a thin metal ribbon mounted in alignmentwith said burner to be transverse to said test flame and to be impingedupon by the inner cone of said flame, a thermo-couple mounted on saidribbon on the side opposite said test burner and in alignment with theinner blue cone of said test flame, and pressure control meansresponsive to said thermo-couple for varying the pressure of the gas insaid gas main.

6. In a device of the character described, a combination of a testburner supplied from a gas main and constructed to produce a blue Bunsenflame with an inner cone, a metal sheet mounted in. front of said burnerto extend transversely of said flame and to have produced upon it a ringof high temperature having a center of-lower temperature, athermo-couple secured to said metal sheet on the side opposite saidburner and inside said ring of high temperature, a voltage responsivedevice connected to said thermo-couple, pressure regulating means forvarying the pres sure of the gas in said gas main, and actuatingmechanism controlled by said voltage responsive device for actuatingsaid pressure regulating means in response to variation in thetemperature of said thermo-couple.

7. In a device of the character described, a test burner connected to agas main, a thin metal ribbon mounted in front of said burner to betransverse to and to be impinged upon by the flame from said burner, athermo-couple secured to said ribbon on the side opposite said burnerand in alignment with theflame from said burner, a pressure regulatingvalve for varying the pressure ofthe gas in said gas main, and valveactuating mechanism comprising a continuously moving motor drivenmember, a valveactuating member connected to said regulating valve, andmeans responsive to voltage variations of said thermo-couple forintermittently connecting said motor driven member and said Valveactuating member to move said regu lating valve in one direction or theother in response to voltage variations of said thermocouple.

In witness whereof, I have hereunto set my hand this 30th day ofSeptember 1925.

- -RONALD S. MoNEIL.

